Diene/nitrile rubbers, commonly called nitrile rubbers or NBR rubbers, are well known. The polymers are cured using sulfur or peroxide cure systems to yield vulcanizates having excellent original physical properties and good oil resistance. Polymer blends of NBR rubbers with other polymers have been proposed in the past. Advantages to be gained by such blends would be, for example, the NBR rubber to impart increased stress-strain properties and oil resistance to EPDM polymers and the EPDM polymer to impart better oxidative and thermal resistance to the NBR in the blend. These advantages have been somewhat obtained in polymer blends where the blending polymer is an unsaturated sulfur-vulcanizable polymer such as SBR rubbers, polyisoprenes, polybutadienes, and EPDM terpolymers. However, these advantages have not been obtained in blends of NBR rubbers with polymers which are typically cured using no sulfur or sulfur donors in the curative system. Examples of these polymers are the halogen-containing polymers such as the epihalohydrin rubbers, the fluoroelastomers, polychloroprene rubbers, halogenated polyolefins, and the like. Such rubbers are cured using curative systems designed to effect crosslinking through the halogen sites on the polymer. Polymer blends of normal NBR rubber with such halogen-containing polymers, cured using the cure systems of the halogenated polymer, exhibit poor phisical properties such as low tensile strength, low abrasion resistance, high oil swell, and the like. The use of dual cure systems, i.e., a cure system for the halogen-containing polymer and a cure system for the NBR rubber, has not provided satisfactory results. Often, the curatives employed in a dual cure system are inactive or interact in the presence of each other, resulting in a very poor cure of the polymer blend.